(a) Field of the Invention
The present invention relates to a motor vehicle with a transversely-disposed engine wherein axes of output shafts of the power plant are extending in the widthwise direction of the vehicle.
(b) Description of the Prior Art
In a front-engine and front-drive car, a power plant is mounted in an engine compartment located in the front portion of a vehicle so as to dispose axes of output shafts of the power plant in the widthwise direction of the vehicle body. In this type of a car with transversely-disposed engine, an axis of output shaft of an engine of the power plant is usually positioned in the forward direction of an axis of output shaft of a differential gear or the center of a front wheel. In this arrangement, however, since the gravitational center of the power plant is positioned in the forward direction of the center of the front wheel, relatively large amount of load is generated due to the weight of the power plant and the moment induced by the weight thereof. This relatively large load acts on the front wheels. As a result, the increased load acting on the front wheels leads to the steering characteristic showing strong understeer propensity. Another disadvantage of the aforementioned arrangement is that flexible designing of the front portion of the vehicle cannot be allowed since the engine is located in the forward position of the front wheels. Furthermore, the wheel housing becomes close to a vehicle cabin because the front wheels are in the rearward position of the engine. This will make the arrangement of various pedals in the front portion of the vehicle difficult and complex.
To solve the above-mentioned probems involving motor vehicles with transversely-disposed engines, especially front-engine and front-drive cars, Japanese Utility Model Application Publication Gazette No. 63-23219 discloses the following arrangement. As shown in FIG. 5, an axis of output shaft x of an engine B constituting a power plant A is positioned in the rearward direction of an axis of output shaft y of a differential gear C or the center z of a front wheel D. A steering member E such as a rack shaft extending in the widthwise direction of the vehicle body to steer the front wheel D is disposed in the forward direction of the power plant A. With this construction, a load acted on the front wheel D is alleviated and thus the excessive understeer propensity of the steering characteristic will be avoided. Flexible design of the front portion of the vehicle and layout of various pedals therein will become possible.
In the arrangement disclosed in the above-mentioned Publication Gazette, a steering system comprising a steering rod F for transmitting the handling of the steering wheel to the steering member E which disposed in the forward direction of the power plant A must be guided to the forward portion of the power plant A through the upper space of a transmission G and the differential gear C of the power plant A. This means that the steering system will be excessively long and must be bended in a complex manner. Furthermore, since the space in the forward portion of the power plant A is rather limited, the layout of the steering member E will be difficult.
The steering rod F is located in the upper direction of the transmission G and the differential gear C. Accordingly, the steering member E is placed in relatively high position. This means that the different in the height between the connecting part of a tie rod which is connected to the steering member E and a lower arm which is a constituent member of the suspension mechanism of the front wheel D will increase. As a result, the problem of a toe angle fluctuation of the front wheels occurs. The toe angle fluctuation is a phenomenon that the toe angle of the front wheels fluctuates when the vehicle bumps or rebounds, causing the deterioration of the steering characteristic. "Bump" refers to the state that the suspension of the front wheels shrinks, causing the front wheels to rise. "Rebound" refers to the state that the suspension of the front wheels extends, causing the front wheels to lower. When the steering member is in the higher position than the lower arm, in the case of bump, the connecting part of the lower arm on the front wheel side travels to the inward direction of the vehicle, and the connecting part of the tie rod on the front wheel side travels to the outward direction of the vehicle. Consequently, the toe angle moves to the inward direction. On the other hand, in the case of rebound, the toe angle moves to the outward direction. In this way, toe angle fluctuation becomes more noticeable when the length of the tie rod becomes shorter and the connecting part of the tie rod on the steering member side becomes higher than the lower arm.